The objective of the proposed research is to determine the role of non-classical molecular pathways mediating estrogenic effects, i.e. pathways that do not rely on direct, ligand-induced activation of the nuclear estrogen receptors (ER) as transcription factors. Specific Aims: (1) Determine the molecular mechanism(s) by which relevant concentrations of xenobiotics act as estrogens; (2) Determine the role of metabolic activation in the non-classical activity of estrogenic compounds. Approach: The ability of test compounds to activate classical and non-classical estrogen signaling pathways will be examined. Pathways to be studied include steroid receptor-mediated transcription, tyrosine kinase/p21ras/MAPK, PI3K/AKT and GPCR30/PKA. The role of metabolic conversion in order to activate these pathways will be assessed. The cytochrome P450 isozymes are suspected of mediating such bioactivation. The impact of different persistent environmental pollutants will be assessed in each molecular pathway and in downstream effects, such as gene expression, apoptosis and cell proliferation.